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The effect of mechanical grinding on the electrochemical properties of Li2Ti3O7 regarding lithium insertion is studied. X-ray diffraction experiments of milling compounds showed a progressively amorphization of the crystalline material due to both crystalline size decreasing and internal strain increasing. These structural modifications are reflected in the electrochemical behavior of Li2Ti3O7, when it is used as the positive electrode in lithium cells. As a function of milling time a higher specific capacity is obtained during the first discharge of the cell, but when charging an increasing in the irreversible capacity is observed. The most promising Li2Ti3O7 based electrode has been achieved, under our experimental conditions, for 13 hours milling that produces a compound with crystallite size of approximately 20 nm. [ABSTRACT FROM AUTHOR]

Abstract: Materials of the series La2−x Sr x NiTiO6−δ (0 ≤ x ≤ 0.5) have been characterized by both structural and electrochemical methods in order to assess their possible use as electrodes for SOFCs. Neutron and X-ray powder diffraction experiments have shown that they are stable under both oxidizing and reducing conditions while chemically compatible with YSZ at SOFC operating temperatures. Moreover, the thermal expansion has been determined to be isotropic with α L = 10.0(3) × 10−6 K−1. This value is similar to that found for other perovskite materials used in SOFCs. However, polarization resistances reveal modest values of electrochemical response under oxygen (1.5 Ω cm2 at 900 °C) and are quite poor in 5%H2/N2 mixtures (15 Ω cm2) at the same temperature. Nevertheless, microstructure has not been optimized fully enough to discard the material as a potential SOFC cathode. [Copyright &y& Elsevier]

Abstract: New olivines LiMAsO4 (M=Mn, Fe, Co, and Ni) have been tested as positive electrode in lithium cells. Under the used experimental conditions we did not succeed to remove lithium ions from LiFeAsO4, LiMnAsO4 or LiNiAsO4. More work is needed in order to verify whether the lack of electrochemical activity is intrinsic to these materials, or it is due to kinetical limitations such as particle size and poor conductivity. On the contrary lithium ions could be reversibly deinserted/inserted from/into LiCoAsO4 at average voltages of 4.8 and 4.6V respectively; the delithiated compound maintaining the olivine structural framework. The high pressure polymorph of LiMAsO4 (M=Fe, Co, Ni) crystallizing with the spinel structure did not show any electrochemical activity potentially useful in rechargeable lithium batteries. [Copyright &y& Elsevier]

Abstract: In the search for new electrodes for lithium batteries processing under high pressure opens new paths to innovative materials. The High Pressure (HP) polymorph of α-FePO4 crystallizes in the CrVO4 structural-type; first principles calculations predict that Li insertion would occur at 3.36V. Accordingly, crystalline samples of HP-FePO4 display electrochemical activity with a lithium insertion process occurring at 3V, which has not been observed in the α-FePO4 polymorph. This reduction process is characterized by a large cell polarization that suggests a very slow kinetics. The poor electrochemical performance of highly crystalline HP-FePO4 is favored in iron phosphate samples obtained under mild conditions of pressure and temperature, that produce a partially amorphous material and prevent an excessive particle growth. [Copyright &y& Elsevier]